The adaptive range of 1/f dynamics in isometric force output was investigated. Participants produced isometric force to targets with predictable demands (constant and sinusoidal) and 1/f noise waveforms (white, pink, brown, and black) that also varied in the frequency bandwidth represented in the force signal (0-4 Hz, 0-8 Hz, and 0-12 Hz). The range of within-trial 1/f force dynamics produced was between darker than pink noise and lighter than black noise according to task conditions. The exponent of the respective 1/f force dynamics decreased as the frequency bandwidth of the force signal increased. The findings reveal an adaptive though restricted range of 1/f force variation that is modulated by the dynamics of the task constraints. (Contains 6 figures.)